2-dimensional image display device, illumination light source and exposure illumination device

ABSTRACT

A 2-dimensional beam scan unit reflects emission beams from a red laser light source, a green laser light source and a blue laser light source and scans in a 2-dimensional direction. Diffusion plates diffuse the respective light beams scanned in the 2-dimensional direction to introduce them to corresponding spatial light modulation elements. The respective spatial light modulation elements modulate the respective lights in accordance with video signals of the respective colors. A dichroic prism multiplexes the lights of the three colors after the modulation and introduces the multiplexed lights to a projection lens so that a color image is displayed on a screen. Since the 2-dimensional light emitted from the beam scan unit is diffused to illuminate the spatial light modulation element, it is possible to change the optical axis of the beam emerging from the light diffusion member for irradiating the spatial light modulation element moment by moment, thereby effectively suppressing speckle noise.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.11/917,986, filed Dec. 18, 2007, which is a National Stage applicationof International Application No. PCT/JP2006/312050, the entireties ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

I. Technical Field

The present invention relates to a 2-dimensional image display device,an illumination light source and an exposure illumination device andalso to a video display device such as a video projector, a televisionreceiver or a liquid crystal panel.

II. Description of the Related Art

In recent years, laser display devices using laser light sources haveattracted more attention. Conventionally, color spectra of fluorescentmaterials are wide and only the subdued color can be obtained even upondisplaying a single color in a television receiver using a cathode-raytube. On the other hand, in a laser display device using laser lightsources, it has become possible to display a very vivid image havinghigh color purity by using laser light sources having suitablewavelengths since lights from the respective light sources aremonochromatic lights.

FIG. 29 shows the schematic construction of a conventional laser displaydevice. Lights from laser light sources 101 a to 101 c of RGB threecolors are intensity-modulated by light modulation elements 106 a to 106c in accordance with an inputted video signal, and multiplexed using amirror 103 and dichroic mirrors 102 a, 102 b. The multiplexed lightspass through a condenser lens 107 and are scanned in x-direction by apolygonal scanner 104 and in y-direction by a galvanometer scanner 105to display a 2-dimensional image on a screen 108. In the display of thisconstruction, since the lights from the RGB light sources aremonochromatic lights, it becomes possible to display a vivid imagehaving high color purity by using laser light sources having suitablewavelengths.

On the other hand, the above laser display device has a problem ofso-called speckle noise that is generated due to the use of laser lightsources having high coherency as light sources. The speckle noise isfine nonuniform noise generated by the interference of scattered lightsfrom the respective parts on the screen 108 when laser beams arescattered on the screen 108. In the above laser display device, thisspeckle noise was removed by vibrating the screen 108.

FIG. 30 shows the schematic construction of another conventional laserdisplay device. Lights from laser light sources 100 a to 100 c of red,green and blue colors are incident on a light integrator 103 afterhaving beam diameters thereof expanded by a beam expander 102. The lightintegrator 103 is an optical system for illuminating rectangularopenings at the top of a spatial light modulation element 107 withuniform illumination intensity and has such a structure that two fly-eyelenses, in each of which rectangular unit lenses are arrayed in a2-dimensional lattice, are arranged in series. Here, uniformillumination by the light integrator 103 is not described in detail.

The light having passed through the light integrator 103 illuminates thespatial light modulation element 107 through a field lens 108 and adiffusion plate 106 after passing through a condenser lens 112 (red andblue lights pass through after being reflected by a mirror 115). Thelights of the respective colors modulated by the spatial lightmodulation element 107 are multiplexed by a dichroic prism 109, and afull color image is formed on a screen 111 by a projection lens 110.

Here, the diffusion plate 106 is a transparent substrate made of groundglass and gives a random phase distribution to the wavefront of theincident light in order to reduce the above speckle noise. If thisdiffusion plate 106 is oscillated by a diffusion plate oscillatingmechanism 113, the phase distribution of the light projected on thescreen 111 changes and the fine pattern of the speckle noise temporallychanges as the diffusion plate 106 moves. If the diffusion plate 106 isoscillated so that a pattern change of the speckle noise is quicker thanthe afterimage time of an observer, the speckle noise is time-averagedby the observer's eyes and a high quality image free from noise issensed. This state of speckle reduction is disclosed in detail, forexample, in Japanese Journal of Applied Physics, Vol. 43, 8B, 2004.

However, in the former laser display device, the screen needs to bevibrated in order to suppress the speckle noise. Thus, it is notpossible to use a fixed wall surface as a screen and to suppress thespeckle noise by an optical system without vibrating the screen.Further, in the latter laser display device, the speckle noise can besuppressed by the optical system, but the beam expander 102, the lightintegrator 103 and the like are necessary to obtain uniformillumination, which complicates the optical system.

-   Patent Literature 1:-   Japanese Examined Patent Publication No. 2003-98601

SUMMARY OF THE INVENTION

An object of the present invention is to provide a 2-dimensional imagedisplay device, an illumination light source and an exposureillumination device capable of obtaining uniform illumination andeffectively suppressing speckle noise using a simple optical system.

One aspect of the present invention is directed to a 2-dimensional imagedisplay device, comprising at least one laser light source; a beam scanunit for converting an emission beam from the laser light source into a2-dimensional light while scanning the emission beam at least in a1-dimensional direction; a spatial light modulation element forspatially modulating the light scanned by the beam scan unit; and alight diffusion member disposed between the beam scan unit and thespatial light modulation element for diffusing the 2-dimensional lightemerging from the beam scan unit.

Since the emission beam from the laser light source is converted intothe 2-dimensional light while being scanned at least in the1-dimensional direction in this 2-dimensional image display device,uniform illumination can be obtained. Further, since the light diffusionmember is disposed between the beam scan unit and the spatial lightmodulation element and the 2-dimensional light emerging from the beamscan unit is diffused and irradiated onto the spatial light modulationelement, the optical axis of the beam emerging from the light diffusionmember to irradiate the spatial light modulation element can be changedmoment by moment and speckle noise can be effectively suppressed. As aresult, a beam expander, a light integrator and the like for uniformillumination become unnecessary, and uniform illumination can beobtained and the speckle noise can be effectively suppressed using asimple optical system.

Another aspect of the present invention is directed to an illuminationlight source, comprising at least one laser light source; a beam scanunit for scanning an emission beam from the laser light source at leastin a 1-dimensional direction; and a light diffusion member for diffusingthe emission beam scanned by the beam scan unit.

In this illumination light source, uniform illumination can be obtainedsince the emission beam from the laser light source is scanned at leastin the 1-dimensional direction. Further, since the emission beam scannedby the beam scan unit is diffused, the optical axis of the beam emergingfrom the light diffusion member can be changed moment by moment,wherefore the speckle noise can be effectively suppressed. As a result,a beam expander, a light integrator and the like for uniformillumination become unnecessary, and uniform illumination can beobtained and the speckle noise can be effectively suppressed using asimple optical system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the construction of a2-dimensional display device according to a first embodiment of theinvention,

FIG. 2 is a conceptual diagram of an optical system for one colorextracted from the 2-dimensional image display device shown in FIG. 1,

FIG. 3 is a diagram showing an illumination beam scanning method in the2-dimensional image display device shown in FIG. 1,

FIG. 4 is a conceptual diagram showing the construction of an opticalsystem for one color extracted from a 2-dimensional image display deviceaccording to a second embodiment of the invention,

FIG. 5 is a diagram showing a suitable range of a light beam diameter ona diffusion plate shown in FIG. 1,

FIG. 6 is a diagram showing light intensity distribution nonuniformityby a 0^(th)-order diffracted light of a holographic optical elementshown in FIG. 5,

FIG. 7 is a diagram showing a light intensity distribution of aholographic optical element having first and second splitting surfacesfor splitting an emission beam from a laser light source shown in FIG. 1at mutually different intervals,

FIG. 8 is a diagram showing a light intensity distribution of aholographic optical element having only the first splitting surfaceshown in FIG. 7,

FIG. 9 is a diagram showing a light intensity distribution of aholographic optical element having only the second splitting surfaceshown in FIG. 7,

FIG. 10 is a schematic diagram showing the construction of an opticalsystem for one color of a 2-dimensional image display device accordingto a third embodiment of the invention,

FIG. 11 is a diagram showing an example of an electro-optical deflectionelement using a polarization inversion element and used as a2-dimensional fine angle beam scan unit shown in FIG. 10,

FIG. 12 is a perspective view showing an example of two 1-dimensionalbeam slitting gratings usable as a 2-dimensional beam splitting gratingshown in FIG. 10,

FIG. 13 is a diagram showing an example of a pseudo random diffusionplate used in a 2-dimensional image display device according to a fourthembodiment of the invention,

FIG. 14 is a schematic diagram showing the construction of an opticalsystem for one color of a 2-dimensional image display device accordingto a fifth embodiment of the invention,

FIG. 15 is a diagram showing a light intensity distribution ofdiffracted lights of a blazed grating shown in FIG. 14,

FIG. 16 is a schematic diagram showing the construction of an opticalsystem for one color of a 2-dimensional image display device accordingto a sixth embodiment of the invention,

FIG. 17 is a schematic diagram showing the construction of an opticalsystem for one color of a 2-dimensional image display device accordingto a seventh embodiment of the invention,

FIG. 18 is a schematic diagram showing the construction of a2-dimensional image display device according to an eighth embodiment ofthe invention,

FIG. 19 is a schematic diagram showing the construction of a MEMS mirrorshown in FIG. 18,

FIG. 20 is a diagram showing a linear beam scanning method in the2-dimensional image display device shown in FIG. 18,

FIG. 21 is a diagram showing an example of the configuration of adisplay region on a spatial light modulation element shown in FIG. 18,

FIG. 22 is a schematic diagram showing the construction of an opticalsystem of the 2-dimensional image display device shown in FIG. 18 inhorizontal direction,

FIG. 23 is a schematic diagram showing the construction of the opticalsystem of the 2-dimensional image display device shown in FIG. 18 invertical direction,

FIG. 24 is a diagram showing an example of a pseudo random diffusionplate used in the 2-dimensional image display device shown in FIG. 18,

FIG. 25 is a schematic diagram showing the construction of an opticalsystem of a 2-dimensional image display device according to a ninthembodiment of the invention in horizontal direction,

FIG. 26 is a schematic diagram showing the construction of the opticalsystem of the 2-dimensional image display device according to the ninthembodiment of the invention in vertical direction,

FIG. 27 is a schematic diagram showing the construction of an opticalsystem of a 2-dimensional image display device according to a tenthembodiment of the invention in horizontal direction,

FIG. 28 is a schematic diagram showing the construction of the opticalsystem of the 2-dimensional image display device according to the tenthembodiment of the invention in vertical direction,

FIG. 29 is a schematic diagram showing the construction of aconventional laser display device, and

FIG. 30 is a schematic diagram showing the construction of anotherconventional laser display device.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention are described withreference to the accompanying drawings.

First Embodiment

FIG. 1 is a schematic construction diagram of a 2-dimensional imagedisplay device according to a first embodiment of the present invention.Laser beams emitted from a red laser light source 1 a, a green laserlight source 1 b and a blue laser light source 1 c are substantiallycondensed by condenser lenses 9 a, 9 b and 9 c, and reflected andtwo-dimensionally scanned by a 2-dimensional beam scan unit 2.

Gas lasers such as He—Ne lasers, He—Cd lasers or Ar lasers orsemiconductor lasers such as AlGaInP semiconductor lasers or GaNsemiconductor lasers or SHG lasers having solid-state lasers asfundamental waves can be used as the laser light sources 1 a, 1 b and 1c. A micromachine moving mirror using a semiconductor process, acombination of a galvanometer mirror and a polygon mirror or the likecan be used as the 2-dimensional beam scan unit 2. It should be notedthat the 2-dimensional beam scan unit 2 is not particularly limited tothe reflection-type 2-dimensional beam scan unit shown in FIG. 1 and maybe a transmission-type 2-dimensional beam scan unit.

Red and blue laser beams reflected by the 2-dimensional beam scan unit 2are reflected by the mirrors 11 a, 11 c, whereas a green laser beam is2-dimensionally scanned on diffusion plates 3 a, 3 b and 3 c after beingdiffused by a concave lens 10. At this time, the respective laser beamsform microspots on the diffusion plates 3 a, 3 b and 3 c since beingsubstantially condensed by condenser lenses 9 a, 9 b and 9 c.

The light beams diffused by the diffusion plates 3 a, 3 b and 3 cilluminate spatial light modulation elements 5 a, 5 b and 5 c whilebeing substantially condensed by field lenses 4 a, 4 b and 4 c. Thefield lenses 4 a, 4 b and 4 c convert the beams having passed throughthe spatial light modulation elements 5 a to 5 c into convergent beamsso that the beams efficiently pass through the aperture of a projectionlens 7. The spatial light modulation elements 5 a, 5 b and 5 c are, forexample, constructed by liquid crystal panels and spatially modulate thebeams of the respective colors in accordance with video signalscorresponding to the respective colors to form 2-dimensional images ofthe respective colors. The beams having passed through the spatial lightmodulation elements 5 a, 5 b and 5 c are multiplexed by a dichroic prism6, and projected on a screen 8 by the projection lens 7.

Next, an illumination method for the spatial light modulation elementsand a state of suppressing speckle noise are described in detail withrespect to FIG. 2 for the operation of the 2-dimensional image displaydevice shown in FIG. 1. FIG. 2 is a conceptual diagram showing anoptical system for one color extracted from the 2-dimensional imagedisplay device shown in FIG. 1. In FIG. 2, the field lenses, thedichroic prism and the like are not shown for simplicity and the2-dimensional beam scan unit 2 is shown to be of the transmission type.

The diffusion plate 3 and the spatial light modulation element 5 aredisposed substantially in parallel at a specified distance L from eachother. The light beam having passed through the 2-dimensional beam scanunit 2 is substantially focused on the diffusion plate 3 to form a lightspot LS. The beam diffused by the diffusion plate 3 irradiates anirradiation region IR shown by a circle in FIG. 2 on the spatial lightmodulation element 5. Only the irradiation region IR of the spatiallight modulation element 5 is projected on the screen 8 by theprojection lens 7 moment by moment, but the irradiation region IR movesto thoroughly scan the spatial light modulation element 5 as the lightspot LS is scanned on the diffusion plate 3 by the 2-dimensional beamscan unit 2. As a result, a 2-dimensional image is entirely displayed onthe screen 8. At this time, if a time for scanning the entire screen isshorter than the afterimage time of human eyes, a viewer can observe theentire 2-dimensional image without becoming conscious of the scanning ofillumination on the screen. Upon displaying moving images, it becomespossible to more smoothly display moving images by scanning the entirescreen within the display period of one frame.

Speckle noise as described in the description of the prior art ispresent in the image projected on the screen 8 at a certain point oftime. When the light spot LS is scanned on the diffusion plate 3 and theposition of the irradiation region IR on the spatial light modulationelement 5 slightly changes, a phase pattern on the diffusion plate 3changes to also change a speckle pattern on the screen 8. For example,if it is assumed that the distance L between the diffusion plate 3 andthe spatial light modulation element 5 is 5 mm and a diffusion angle(full-angle-half-power) of the diffusion plate 3 is 10°, the size(diameter of the irradiation region IR) D of the irradiation region onthe spatial light modulation element 5 is 5 mm×tan(10°)=about 880micrometers. Conversely, one specific point on the spatial lightmodulation element 5 continues to be irradiated only for a period duringwhich the light spot LS moves 880 micrometers on the diffusion plate 3.

Here, if the size of the light spot LS on the diffusion plate 3 isassumed to be 50 micrometers, 17 (=880 micrometers÷50 micrometers) ormore different speckle patterns are generated while the specific pointis irradiated. As a result, upon observing a projected image, a2-dimensional image having the speckle noise suppressed can be observedsince these speckle patterns are time-averaged. At this time, thesmaller the spot size on the diffusion plate 3, the quicker the specklepattern changes to be time-averaged. Therefore, the visible specklenoise can be more suppressed.

A spacing d of the tracks of the light spot LS on the diffusion plate 3is an important factor contributing to the uniformity of the intensityof a displayed image. In order to realize a uniform intensitydistribution, the spacing d preferably satisfies a relationshipd≦2×L×tan(θ/2) if L, θ denote a distance between the diffusion plate 3and the spatial light modulation element 5 and the diffusion angle(full-angle-half-power of the diffusion angle of an emerging beam when aparallel beam is incident on the diffusion plate) θ by the diffusionplate 3.

Further, the diffusion angle θ of the diffusion plate is restricted byan f-number of the projection lens 7.

Specifically, a beam having a diffusion angle exceeding 1/f radian withrespect to the f-number of the projection lens 7 is blocked by theprojection lens 7. Accordingly, in order to ensure sufficient lightutilization efficiency, the diffusion angle θ of the diffusion plate 3may be set to about 2×tan⁻¹(1/2f) or smaller. Conversely, upon using,for example, the diffusion plate 3 having a diffusion angle of 10°, thef-number of the projection lens 7 is preferably (2×tan(10°/2))⁻¹=5.7 orsmaller and, for example, preferably about 5.

As described above, in this embodiment, the speckle noises of the lightsof the respective colors can be suppressed and the intensity of thedisplayed image can be made uniform while ensuring sufficientutilization efficiencies for the respective lights. Therefore, asatisfactory full color video image can be displayed on the screen 8.

A feature of the 2-dimensional image display device shown in FIG. 1 isthat the optical axes of the emission beams from the respective laserlight sources 1 a, 1 b and 1 c mutually differ relative to the2-dimensional beam scan unit 2, i.e. the emission beams from therespective laser light sources 1 a, 1 b and 1 c are incident on the2-dimensional beam scan unit 2 at mutually different angles. Thedichroic mirrors 102 a, 102 b are used to align the optical axes of theemission beams from the laser light sources 101 a to 101 c of threecolors in the conventional laser display device shown in FIG. 29,whereas the optical axes of the emission beams from the laser lightsources 1 a, 1 b, 1 c can be set in different directions in thisembodiment. Thus, the dichroic mirrors for multiplexing becomeunnecessary and the 2-dimensional image display device can be realizedby a simple optical system.

Another feature of the 2-dimensional image display device shown in FIG.1 is that uniform illumination can be obtained without using acomplicate optical component such as a light integrator between the2-dimensional beam scan unit 2 and the diffusion plates 3. For example,in a presently commercially available projector using a discharge tubeas a light source, illumination is made uniform using a light integratorincluding two lens arrays. However, in this embodiment, uniformillumination can be realized without using a large optical component andwithout depending on the intensity distribution of the emission beamfrom the light source.

Although such a scanning method for high-speed scanning in thehorizontal direction and low-speed scanning in the vertical direction inthe 2-dimensional beam scan unit 2 is shown in FIG. 2, it is possible tosuppress a scanning speed by scanning in a lattice pattern as shown inFIG. 3. FIG. 3 is a diagram showing an example of tracks of the lightspots LS on the diffusion plate 3 at the time of scanning using atriangular wave whose ratio of a scan frequency in vertical direction tothe one in horizontal direction is 15:19. By scanning the emission beamsfrom the laser light sources 1 a, 1 b and 1 c with such a frequency atwhich a ratio of the scan frequency in vertical direction to the one inhorizontal frequency is a ratio of integers prime to each other, adifference between the scanning speeds in horizontal and verticaldirections can be made smaller. Therefore, the construction of the2-dimensional beam scan unit 2 can be simplified and the diffusionplates 3 can be uniformly illuminated.

Second Embodiment

Next, a second embodiment of the present invention is described. FIG. 4is a schematic construction diagram of an optical system for one colorextracted from a 2-dimensional image display device according to thesecond embodiment of the present invention. Since the 2-dimensionalimage display device according to the second embodiment is the same asthe one shown in FIG. 1 except the construction shown in FIG. 4, thesame parts are neither shown nor described in detail.

In the second embodiment, instead of the 2-dimensional beam scan unit 2shown in FIG. 2, a 1-dimensional beam splitting grating 12 and a1-dimensional beam scan unit 15 are used as shown in FIG. 4. Forexample, a holographic optical element (HOE) or the like can be used asthe 1-dimensional beam splitting grating 12, and a galvanometer mirroror the like can be used as the 1-dimensional beam scan unit 15.

In the above construction, after passing through a condenser lens 9, alight beam from a laser light source 1 is 1-dimensionally scanned in the1-dimensional beam scan unit 15 and then incident on the 1-dimensionalbeam splitting grating 12. The 1-dimensional beam splitting grating 12is, for example, a diffraction grating in which a 1-dimensionalconvexo-concave pattern is formed on a transparent substrate made of,e.g. glass and can split the incident light beam into a multitude oflight beams having the same power by optimizing the cross-sectionalshape of the grating.

A plurality of light beams split by the 1-dimensional beam splittinggrating 12 become a light spot array LL as a 1-dimensional multibeamarray, in which the plurality of light beams are vertically arrayed in arow, on a diffusion plate 3. At this time, since the light beam from thelaser light source 1 is scanned in horizontal direction by the1-dimensional beam scan unit 15, the light spot array LL is scanned in adirection perpendicular to a light diffraction direction and, when theposition of an irradiation region IR on a spatial light modulationelement 5 slightly changes, a phase pattern on the diffusion plate 3changes to also change a speckle pattern generated on a screen 8.

In this way, the same effects as at the time of 2-dimensional scanningon the diffusion plate 3, i.e. the effects similar to those of the firstembodiment can also be obtained in this embodiment. Further, since thescan direction is 1-dimensional and the scan frequency is small in thisembodiment, the miniaturization, lower power consumption and lower costof the 1-dimensional beam scan unit 15 can be realized.

Further, a light beam diameter S on the diffusion plate 3 preferablysatisfies a relationship S>L((−d if (, L and d denote the diffusionangle of the diffusion plate 3, a distance between the diffusion plate 3and the spatial light modulation element 5 and the spacing between theadjacent light beams on the diffusion plate 3. FIG. 5 is a diagramshowing a suitable range of the light beam diameter S on the diffusionplate 3 shown in FIG. 4. It should be noted that only two adjacent lightbeams out of a plurality of diffracted beams are shown in FIG. 5 tofacilitate the description.

In the case of using a holographic optical element 12 a as the1-dimensional beam splitting grating 12 as shown in FIG. 5, theholographic optical element 12 a causes a light beam B0 to be incidenton the diffusion plate 3 while splitting it into a plurality of lightbeams. Out of the plurality of light beams, light beams B1, B2 emergingwhile defining the largest angle therebetween are shown. Here, if it isassumed that S denotes the diameter of the light beams B1, B2 on thediffusion plate 3, d the spacing between these light beams, (thediffusion angle of the diffusion plate 3 and L the distance between thediffusion plate 3 and the spatial light modulation element 5, the lightbeam B1 illuminates a region R1 on the spatial light modulation element5, the light beam B2 illuminates a region R2 on the spatial lightmodulation element 5 and the light beams B1, B2 overlap in a region R3.Accordingly, if the light beam diameter S on the diffusion plate 3satisfies the relationship S>L((−d, any arbitrary point on the spatiallight modulation element 5 is illuminated by a diffused light of theplurality of light beams, wherefore the speckle noise can be reduced.

It is preferable to use a holographic optical element having first andsecond splitting surfaces for splitting an emission beam from the laserlight source 1 at mutually different intervals as the 1-dimensional beamsplitting grating 12. FIG. 6 is a diagram showing light intensitydistribution nonuniformity cased by a 0^(th)-order light of theholographic optical element 12 a shown in FIG. 5. As shown in FIG. 6, alight intensity distribution LD on the diffusion plate 3 has a peak by a0^(th)-order diffracted light L0 and a peak P0 appears in a lightintensity distribution LI on the spatial light modulation element 5 inthe case of using the holographic optical element 12 a. Thus, the lightintensity distribution LI on the spatial light modulation element 5becomes nonuniform.

FIG. 7 is a diagram showing a light intensity distribution of aholographic optical element having first and second splitting surfacesfor splitting an emission beam from the laser light source 1 shown inFIG. 1 at mutually different intervals, FIG. 8 is a diagram showing alight intensity distribution of a holographic optical element havingonly the first splitting surface shown in FIG. 7, and FIG. 9 is adiagram showing a light intensity distribution of a holographic opticalelement having only the second splitting surface shown in FIG. 7.

As shown in FIG. 7, a holographic optical element 12 b has a firstsplitting surface F1 for splitting an emission beam from the laser lightsource 1 at first intervals and a second splitting surface F2 forsplitting the emission beam from the laser light source 1 at secondintervals wider than the first intervals. In the case of using aholographic optical element 12 c having only the first splitting surfaceF1 as shown in FIG. 8, the 0^(th)-order diffracted light L0 causes thenonuniformity of the light intensity distribution as shown. Also in thecase of using a holographic optical element 12 d having only the secondsplitting surface F2 as shown in FIG. 9, the 0^(th)-order diffractedlight L0 causes the nonuniformity of the light intensity distribution asshown.

However, since the first and second splitting surfaces F1, F2 aresimultaneously used in the holographic optical element 12 b shown inFIG. 7, the light intensity distributions of both are combined. As aresult, the light intensity distribution on the diffusion plate 3 of thelight beam split by the holographic optical element 12 b becomes thelight intensity distribution LD shown in FIG. 7, whereby thenonuniformity of the light intensity distribution caused by the0^(th)-order diffracted light can be made smaller. The first and secondsplitting surfaces are not particularly limited to those formed on thefront and rear surfaces of the holographic optical element 12 b asdescribed above, and two, three or more of the holographic opticalelements 12 c, 12 d shown in FIGS. 8 and 9 may be juxtaposed. Thesepoints also hold for other embodiments described later.

The method for 1-dimensionally expanding the light beam is notparticularly limited to the above example, and it is also possible touse a cylindrical lens to be described later instead of the1-dimensional beam splitting grating 12 of FIG. 4. In this case, alinear light beam illuminates the diffusion plate 3 instead of the lightspot array LL.

Third Embodiment

Next, a third embodiment of the present invention is described. FIG. 10is a conceptual diagram of an optical system for one color extractedfrom a 2-dimensional image display device according to the thirdembodiment of the present invention. Since the 2-dimensional imagedisplay device according to the third embodiment is the same as the oneshown in FIG. 1 except the construction shown in FIG. 10, the same partsare neither shown nor described in detail.

In the third embodiment, instead of the 2-dimensional beam scan unit 2shown in FIG. 2, a 2-dimensional beam splitting grating 17 and a2-dimensional fine angle beam scan unit 16 are used as shown in FIG. 10.In this construction, a light beam from a laser light source 1 is finelyscanned in 2-dimensional directions in the 2-dimensional fine angle beamscan unit 16 and then incident on the 2-dimensional beam splittinggrating 17 after passing through a condenser lens 9. The 2-dimensionalbeam splitting grating 17 is a diffraction grating having a2-dimensional convexo-concave pattern formed on a transparent substratemade of, e.g. glass similar to the 1-dimensional beam splitting grating12 of the second embodiment. The 1-dimensional beam splitting grating 12has a 1-dimensional strip-like convexo-concave shape, whereas thesurface shape of the 2-dimensional beam splitting grating 17 has a2-dimensional distribution and can split an incident light beam into amultitude of light beams having the same power by optimizing thecross-sectional shape of the grating.

A conventional technology known as a diffractive optical element or aholographic optical element can be used for the 2-dimensional beamsplitting grating 17, and its design method and production method aredisclosed in detail, for example, “Diffractive Optics Design,Fabrication and Test” by Donald C O'Shea et al., SPIE PRESS(2004)ISBN:0-8194-5171-1.

A plurality of light beams split by the 2-dimensional beam splittinggrating 17 become a 2-dimensional multibeam SM on the diffusion plate 3by being arrayed in vertical and horizontal directions. At this time,since the light beam from the laser light source 1 is finely scanned invertical and horizontal directions by the 2-dimensional fine angle beamscan unit 16, the 2-dimensional multibeam SM is also finely scanned invertical and horizontal directions and, when an irradiation region IR ona spatial light modulation element 5 slightly changes, a phase patternon a diffusion plate 3 changes to also change a speckle patterngenerated on a screen 8.

In this way, the same effects as at the time of 2-dimensional scanningon the diffusion plate 3, i.e. the effects similar to those of the firstembodiment can also be obtained in this embodiment. Further, in thisembodiment, the beam is split to illuminate substantially the entiresurface of the diffusion plate 3 by the 2-dimensional beam splittinggrating 17, and a range scanned by the 2-dimensional fine angle beamscan unit 16 may be a small range having a dimension about equal to thespacing between the adjacent light spots. Since a beam scan anglebecomes remarkably small in this embodiment, the miniaturization, lowercost, lower power consumption and lower noise of the 2-dimensional fineangle beam scan unit 16 can be realized.

Further, an acousto-optic device having no large scan angle, anelectro-optical deflection element using a polarization inversionelement and the like can be used as the 2-dimensional fine angle beamscan unit 16. FIG. 11 is a diagram showing an example of anelectro-optical deflection element using a polarization inversionelement and used as the 2-dimensional fine angle beam scan unit 16 shownin FIG. 10.

Electro-optical crystal substrates 20 a, 20 b shown in FIG. 11 arepolarization inversion elements, wherein the electro-optical crystalsubstrate 20 a scans a light beam in horizontal direction and theelectro-optical crystal substrate 20 b scans the light beam, which isbeing scanned in horizontal direction, further in vertical directionupon the application of a specified alternating-current voltage.

For example, lithium niobate or lithium tantalate can be used as thematerial of the electro-optical crystal substrates 20 a, 20 b. Theelectro-optical crystal substrates 20 a, 20 b are carved outperpendicularly to optical axes thereof, and the polarizations oftriangular regions within substrate surfaces are inverted to formpolarization inversion regions 21 a, 21 b. Since the optical axes areinverted in the polarization inversion regions 21 a, 21 b,electro-optical effects having polarities opposite to those ofsurrounding regions are shown.

Further, top-surface electrodes 22 a, 22 b and under-surface electrodes23 a, 23 b are formed on the top and under surfaces of theelectro-optical crystal substrates 20 a, 20 b, and electric fields areapplied in optical axis directions (directions normal to the substrates)by alternating-current power supplies 24 a, 24 b. At this time, asdescribed above, a refractive index change occurs between thepolarization inversion regions 21 a, 21 b and their surrounding areas bythe electro-optical effects, and the electro-optical crystal substrates20 a, 20 b act like prisms, so to speak, thereby being able to deflectthe light passing through the substrates. Further, deflection in anopposite direction is possible by reversing an application direction ofthe electric field.

The characteristics of the electro-optical crystal substrates 20 a, 20 bare to be highly reliable, silent and speedy by having no movableportions. On the other hand, the disadvantage thereof is to require highvoltages to ensure large angle of deflection. However, since an angle ofdeflection necessary for the 2-dimensional image display device of FIG.10 is 1° or smaller, the light beam can be deflected in horizontal andvertical directions by the electro-optical crystal substrates 20 a, 20 bwith practical drive voltages within this range.

The 2-dimensional beam splitting grating 17 is not particularly limitedto the above example, and two 1-dimensional beam splitting gratings madeof holographic optical elements may be used. FIG. 12 is a perspectiveview showing an example of two 1-dimensional beam splitting gratingsusable as the 2-dimensional beam splitting grating 17 shown in FIG. 10.As shown in FIG. 12, a 1-dimensional beam splitting grating 17 a splitsan incident light beam into a plurality of light beams having the samepower and arrayed in horizontal direction, and a 1-dimensional beamsplitting grating 17 b splits each of the plurality of beams split inhorizontal direction into a plurality of light beams having the samepower in vertical direction. As a result, similar to the 2-dimensionalbeam splitting grating 17, a 2-dimensional multibeam in which theplurality of light beams are arrayed in vertical and horizontaldirections can be generated on the diffusion plate 3. As a result, thesame effects as the 2-dimensional beam splitting grating 17 can beobtained and the nonuniformity of the light intensity distributioncaused by the 0^(th)-order diffracted light can be reduced similar tothe holographic optical element 12 b shown in FIG. 7.

Fourth Embodiment

Next, a fourth embodiment of the present invention is described. FIG. 13is a diagram showing an example of a pseudo random diffusion plate usedin a 2-dimensional image display device according to the fourthembodiment of the present invention. Since the 2-dimensional imagedisplay device according to the fourth embodiment is the same as the oneshown in FIG. 1 except the use of a pseudo random diffusion 3 a plateshown in FIG. 13 as the diffusion plate 3, the same parts are neithershown nor described in detail.

The diffusion plate 3 shown in FIG. 2 is fabricated by randomlyroughening the top surface of a transparent substrate normally made ofglass, resin or the like, whereas the pseudo random diffusion plate 3 ashown in FIG. 13 is fabricated by forming a latticed convexo-concavepattern on the top surface of a transparent substrate. The top surfaceof the pseudo random diffusion plate 3 a is divided into 2-dimensionallatticed cells CE, and the depths of the convexo-concave pattern arerandomly set so that the phases of lights passing through the respectivecells CE randomly change. The maximum depth may be set to λ/(n−1).

An advantage of using the pseudo random diffusion plate 3 a shown inFIG. 13 is that a diffusion angle of the light passing through thepseudo random diffusion plate 3 a can be strictly controlled by the sizeof the cells CE. Specifically, the light is diffused to have anintensity distribution I(θ)={sin(α)/α}² (α=θ×dc/(π·λ)) if dc and (denotethe cell interval of the latticed cells CE and an angle. For example, inorder to fabricate a diffusion plate whose full-angle-half-power is 10(,I(( )=½ is substituted into the above equation to obtain the cell pitchdc corresponding to a wavelength (. For example, in the case of usingblue, green and red light sources having wavelengths (=0.473, 0.532 and0.640 micrometers respectively, fabrication may be made to have cellintervals dc of 2.4, 2.7 and 3.2 respectively.

On the other hand, since the surface shapes of normal diffusion platesare random, there are problems that (1) light utilization efficiencydecreases because angles of diffusion locally differ depending on spots,(2) intensity distribution nonuniformity appears in an image becausetransmittance changes depending on spots and (3) it is difficult tostably fabricate in such a manner as to have a constant diffusion angle.The normal diffusion plates have another problem of disrupting adeflection direction when a large diffusion angle is taken. The pseudorandom diffusion plate 3 a shown in FIG. 13 can solve these problems.

The pseudo random diffusion plate 3 a of FIG. 13 can be fabricated byforming a convexo-concave pattern on a glass plate by a photolithographymethod and an etching method used in a normal semiconductor process. Atthis time, if a phase transition is selected to be, for example, 0, π/2,π, 3π/2 as in FIG. 13, the pseudo random diffusion plate 3 a can beeasily fabricated by two etching processes corresponding to the phasetransitions to π/2 and to π.

Fifth Embodiment

Next, a fifth embodiment of the present invention is described. FIG. 14is a conceptual diagram of an optical system for one color extractedfrom a 2-dimensional image display device according to the fifthembodiment of the present invention. Since the 2-dimensional imagedisplay device according to the fifth embodiment is the same as the oneshown in FIG. 1 except the construction shown in FIG. 14, the same partsare neither shown nor described in detail.

In the fifth embodiment, a blazed grating 17 c and a light shieldingplate 18 are used as shown in FIG. 14 instead of the 2-dimensional beamsplitting grating 17 shown in FIG. 10.

In this construction, a light beam from a laser light source 1 is finelyscanned in 2-dimensional directions in a 2-dimensional fine angle beamscan unit 16 and then incident on the blazed grating 17 c after passingthrough a condenser lens 9. The blazed grating 17 c is a 2-dimensionaldiffraction grating in which a 2-dimensional wedge-shaped pattern isformed on a transparent substrate made of, e.g. glass so that therespective grating surfaces (emergent surfaces) are inclined withrespect to the incident surface similar to the 2-dimensional beamsplitting grating 17 of the third embodiment. Accordingly, out of thelight beam emerging from the blazed grating 17 c, only a 0^(th)-orderdiffracted light is introduced in a direction normal to the incidentsurface (in the central axis direction of the blazed grating 17 c) to beincident on the light shielding plate 18. On the other hand, theremaining diffracted lights are deflected by a specified angle inrightward direction (toward the right side in FIG. 14) to be incident ona diffusion plate 3 located at a position displaced only by a specifieddistance from the central axis of the blazed grating 17 c in rightwarddirection. Since the action after the diffusion plate 3 is similar tothe one in the third embodiment, it is not described.

FIG. 15 is a diagram showing a light intensity distribution of thediffracted lights of the blazed grating 17 c shown in FIG. 14. As shownin FIG. 15, the blazed grating 17 c has a plurality of grating surfacesF2 having randomly different heights, and an angle defined between therespective grating surfaces F2 and an incident surface F1 is set to aspecified angle θ (e.g. 30°). If a light beam is incident on the blazedgrating 17 c formed as above, a 0^(th)-order diffracted light L0emerging from an edge portion EG of each grating surface irradiates thelight shielding plate 18 and diffracted lights L1 other than the0^(th)-order diffracted light irradiate the diffusion plate 3 with auniform light intensity distribution as shown.

As described above, in this embodiment, effects similar to those of thethird embodiment can be obtained and, since the 0^(th)-order diffractedlight irradiates neither the diffusion plate 3 nor the spatial lightmodulation element 5, the light intensity distribution on the spatiallight modulation element 5 can be made more uniform.

Sixth Embodiment

Next, a sixth embodiment of the present invention is described. FIG. 16is a conceptual diagram of an optical system for one color extractedfrom a 2-dimensional image display device according to the sixthembodiment of the present invention. Since the 2-dimensional imagedisplay device according to the sixth embodiment is the same as the oneshown in FIG. 1 except the construction shown in FIG. 16, the same partsare neither shown nor described in detail.

In the sixth embodiment, a beam vibrator 19 for vibrating a2-dimensional beam splitting grating 19 a is used as shown in FIG. 16instead of the 2-dimensional beam scan unit 2 shown in FIG. 2. In thisconstruction, a light beam from a laser light source 1 is reflected bythe 2-dimensional beam splitting grating 19 a of the beam vibrator 19 tobe introduced to a diffusion plate 3 after passing through a condenserlens 9.

The beam vibrator 19 includes a vibratory mirror such as a MEMS (MicroElectro Mechanical Systems) mirror, and is constructed such that the2-dimensional beam splitting grating 19 a formed on a mirror surface isso supported on a support 19 b as to be capable of 1-dimensional or2-dimensional minute vibration. Thus, the 2-dimensional beam splittinggrating 19 a is 1-dimensionally or 2-dimensionally minutely vibratedsimilar to a MEMS mirror to be described later. The 2-dimensional beamsplitting grating 19 a is a diffraction grating having a 2-dimensionalconvex-concave pattern formed on the mirror surface similar to the2-dimensional beam splitting grating 17 shown in FIG. 10, and reflectsan incident beam to split it into a multitude of light beams having thesame power.

A plurality of light beams split by the 2-dimensional beam splittinggrating 19 a become a 2-dimensional multibeam SM on the diffusion plate3 by being arrayed in vertical and horizontal directions. At this time,since the 2-dimensional beam splitting grating 19 a is minutely vibratedby the beam vibrator 19, the 2-dimensional multibeam SM is also minutelyscanned in vertical and/or horizontal direction and, when an irradiationregion IR on a spatial light modulation element 5 slightly changes, aphase pattern on the diffusion plate 3 changes to also change a specklepattern generated on a screen 8.

As described above, in this embodiment, effects similar to those of thefirst embodiment can be obtained and, since the 2-dimensional beamsplitting grating 19 a is integral to the beam vibrator 19, the numberof components can be reduced and the device can be further miniaturized.

Seventh Embodiment

Next, a seventh embodiment of the present invention is described. FIG.17 is a conceptual diagram of an optical system for one color extractedfrom a 2-dimensional image display device according to the seventhembodiment of the present invention. Since the 2-dimensional imagedisplay device according to the seventh embodiment is the same as theone shown in FIG. 1 except the construction shown in FIG. 17, the sameparts are neither shown nor described in detail. Further, in order tofacilitate the diagrammatic representation, only a polygon scanner isshown as a 2-dimensional scan unit.

In the seventh embodiment, a polygon scanner 21 and a galvanometermirror (or polygon scanner, not shown) are used as a 2-dimensional beamscan unit 2, and reflection mirrors 22 are added to surround an opticalpath between the polygon scanner 21 and a diffusion plate 3 and anoptical path between the diffusion plate 3 and a spatial lightmodulation element 5.

In this construction, a light beam from a laser light source 1 isreflected by the galvanometer mirror to be scanned and is furtherreflected by the polygon scanner 21 to be scanned. The light beamreflected by the polygon scanner 21 is reflected a plurality of timesbetween the reflection mirrors 22 and finally introduced to a field lens4, the diffusion plate 3 and the spatial light modulation element 5. Asa result, effects similar to those of the first embodiment can beobtained in this embodiment as well.

Here, in the case of a polygon mirror having a small number ofreflection surfaces, e.g. eight surfaces like the polygon scanner 21, ascan angle of the light beam becomes larger, wherefore it becomesdifficult to design the optical system without being able to ensure asufficient distance between the polygon scanner 21 and the spatial lightmodulation element 5. On the other hand, since the light beam isreflected by the reflection mirrors in this embodiment, a sufficientdistance can be ensured between the polygon scanner 21 and the spatiallight modulation element 5 and, hence, the optical system can be easilydesigned. Generally, a polygon scanner having a smaller number ofreflection surfaces is easier to fabricate and has lower cost.

Further, since the polygon scanner 21 has a rotating mechanism to makerotary motions in one direction, the scan speed of the light beam can bemade constant from the start to the end and the light intensitydistribution on the spatial light modulation element 5 can be made moreuniform as compared to a vibrating mechanism to make reciprocal motions.Furthermore, since the optical path between the polygon scanner 21 andthe diffusion plate 3 and the one between the diffusion plate 3 and thespatial light modulation element 5 are covered by the reflection mirrors22, the loss of the light beam in this part can be prevented and thelight intensity distribution on the spatial light modulation element 5can be improved.

Although the example of using the 2-dimensional beam scan unit and thereflection mirrors 22 is shown above, similar effects can be obtainedeven if reflection mirrors are used with a 1-dimensional beam scan unit,a 1-dimensional beam splitting portion and the like.

Eighth Embodiment

Next, an eighth embodiment of the present invention is described. FIG.18 is a schematic construction diagram of a 2-dimensional image displaydevice according to the eighth embodiment of the present invention.Lights emitted from a red laser light source 1 a, a green laser lightsource 1 b and a blue laser light source 1 c are expanded in horizontaldirection by concave lenses 8 to irradiate a MEMS mirror 9. The MEMSmirror 9 has three mirror portions 91 whose vertical angles areindependently variable, and the lights emitted from the red laser lightsource 1 a, the green laser light source 1 b and the blue laser lightsource 1 c are incident on the respective mirror portions 91. The lightsreflected by the mirror portions 91 pass through a diffusion plate 3disposed before and proximate to a spatial light modulation element 5and illuminate the spatial light modulation element 5 as linear beams 13a, 13 b and 13 c. The lights modulated by the spatial light modulationelement 5 are projected onto a screen 7 by a projection lens 6 to forman image.

FIG. 19 is a schematic construction diagram of the MEMS mirror 9 shownin FIG. 18. The MEMS mirror 9 is formed by adhering the mirror portions91 formed integral to supports 97 to a silicon substrate 90 having upperelectrodes 94, lower electrodes 95 and a bonding pad 96 formed in arecess thereof via an insulation film 93. The mirror portions 91 and thesilicon substrate 90 having such structures can be fabricated using thephotolithography technology and the etching technology.

The mirror portions 91 are connected to the silicon substrate 90 via thesupports 97. Below the mirror portions 91, the upper electrodes 94 andthe lower electrodes 95 are formed on the silicon substrate 90 via theinsulation film 93. The respective electrodes are electrically connectedto the bonding pad 96, but wirings therebetween are not shown forsimplicity. Reflection films 92 for improving reflectance are mountedabove the mirror portions 91.

An electrically conductive material is used for the silicon substrate90, and an electrostatic force acts in a direction to bring the siliconsubstrate 90 and the upper electrode 94 toward each other and the mirrorportion 91 is so inclined as to face upward upon the application of avoltage between the silicon substrate 90 and the upper electrode 94.Conversely, upon the application of a voltage between the siliconsubstrate 90 and the lower electrode 95, an electrostatic force acts ina direction to bring the silicon substrate 90 and the lower electrode 95toward each other and the mirror portion 91 is so inclined as to facedownward. A moment of force in a direction to rotate the mirror portion91 is determined by a difference between the voltage between the upperelectrode 94 and the silicon substrate 90 and the voltage between thelower electrode 95 and the silicon substrate 90.

If the mirror portion 91 is inclined, the support 97 is twisted and amoment of force acts in such a direction as to reduce the inclination.If a direct-current voltage is applied to the upper electrode 94 and thelower electrode 95, the angle of the mirror portion 91 is so determinedas to balance out an electrostatic force and a torsional moment. Inorder to dynamically control the angle of the mirror portion 91 as inthe 2-dimensional image display device of this embodiment, the timewaveform of the applied voltage is determined in consideration of theinertia moment of the mirror portion 91 and the air resistance of themirror portion 91 in addition to the electrostatic force and thetorsional stress of the support 97.

The MEMS mirror 9 formed with the mirror portions 91 with a width of 800microns and a length of 3 mm was fabricated. A primary resonancefrequency in this case was 25 kHz. Pulse voltages were applied inopposite directions near a scan starting position and near a scan endingposition as drive voltages so as to enable linear scanning at high speedin relation to time. The timings of the applied pulses were controlledin accordance with a signal from a photodetector 17. As a result, theMEMS mirror 9 having good scanning characteristics could be fabricated.

The upper and lower electrodes 94, 95 can also be used as a detector foran angle of rotation by not only applying the drive voltages thereto asdescribed above, but also detecting an electrostatic capacity betweenthe respective electrodes 94, 95 and the mirror portion 91. For example,the angle of rotation of the mirror portion 91 can be known by detectinga current value with a high-frequency voltage applied to the respectiveelectrodes. By using the MEMS mirror 9 for the detection of the angle ofrotation of the mirror in this way, the 2-dimensional image displaydevice may be realized by a simple construction without using theaforementioned photodetector 17.

Although the MEMS mirror 9 using an electrostatic force as a drive forceis taken as an example in this embodiment, any construction isapplicable provided that it can scan a light beam. For example, a beamscanning mechanism using the Lorentz force of a magnetic coil may beused. In this case, a counter voltage of the coil is detected to detectthe rotating speed of the mirror portion 91, and the detection resultcan be used for the angle control of the mirror portion 91. It is alsopossible to utilize a beam scanning mechanism taking advantage ofelectrostrictive effects brought about by the use of a piezoelectricfilm. In this case, the angle of rotation of the mirror portion 91 canbe detected utilizing the piezoelectric effects of the piezoelectricfilm and the detection result can be used for the angle control of themirror portion 91.

A feature of this embodiment is that images of red, green and bluelights can be projected onto the screen using one spatial lightmodulation element 5 by a method described below to obtain a full colorimage.

The angles of rotation of the three mirror portions 91 provided in theMEMS mirror 9 are vertically variable, and these respective angles areindependently controlled by a timing controller 16. The red laser beam,the green laser beam and the blue laser beam incident on the respectivemirror portions 91 are projected to have linear shapes at differentvertical positions on the spatial light modulation element 5. An imageprocessor 15 separates a video signal inputted from the outside into ared video signal, a green video signal and a blue video signal, andfeeds the different video signals to different vertical regions of thespatial light modulation element 5. In other words, out of the videosignal, signals corresponding to the respective color images are fed tothe regions to be irradiated by the respective laser beams.

The linear beams 13 a to 13 c on the spatial light modulation element 5vertically move on the spatial light modulation element 5 as the mirrorportions 91 of the MEMS mirror 9 are driven. At this time, the timingcontroller 16 controls the image processor 15 and the MEMS mirror 9 sothat a red image 14 a is constantly displayed in the region of thespatial light modulation element 5 irradiated with the red linear beam13 a, a green image 14 b is constantly displayed in the region of thespatial light modulation element 5 irradiated with the green linear beam13 b and a blue image 14 c is constantly displayed in the region of thespatial light modulation element 5 irradiated with the blue linear beam13 c.

A state of scanning the linear beams 13 a to 13 c at this time isconceptually shown in FIG. 20. Tracks Ta, Tb and Tc respectively shownin dashed dotted line, solid line and broken line represent the tracksof the red linear beam 13 a, the green linear beam 13 b and the bluelinear beam 13 c, and the red, green and blue linear beams 13 a, 13 band 13 c are driven to have triangular waveforms on the spatial lightmodulation element 5. It is ideally desirable to drive them to havesawtooth waveforms, but it is not possible to instantaneously move themirror portions 91 of the MEMS mirror 9 due to the rotational momentsthereof and the mirror portions 91 are actually driven by asymmetrictriangular waveforms as shown and the positions of the linear beams 13 ato 13 c accordingly change along asymmetric triangular paths. FIG. 20 isa schematic diagram. In reality, the motions of the beams are disrupted,for example, due to overshoots seen at turn-round positions due to theinertia moments of the mirror portions 91. The triangular tracks areshown as the tracks of the respective linear beams 13 a to 13 c withoutshowing these disrupted points.

In the example of FIG. 20, the respective linear beams 13 a to 13 c arescanned to illuminate the spatial light modulation element 5 while beingmoved from the left side (lower side in FIGS. 18 and 20) toward theright side (upper side in FIGS. 18 and 20) on the spatial lightmodulation element 5. When the respective linear beams 13 a to 13 creach the rightmost side of the spatial light modulation element 5, thetiming controller 16 turns off the laser light sources 1 a to 1 cemitting the respective beams and causes the MEMS mirror 9 to move therespective linear beams 13 a to 13 c to the rightmost side of thespatial light modulation element 5 at high speeds.

Specifically, the timing controller 16 causes the laser light sources toemit the respective beams when the respective tracks Ta, Tb and Tc arediagonally right up while prohibits the laser light sources fromemitting the respective beams when the respective tracks Ta, Tb and Tcare diagonally right down. By a control as described above, the redlaser light source 1 a, the green laser light source 1 b and the bluelaser light source 1 c are successively turned on during light emissionperiods La to Lc, respectively, and the respective linear beams 13 a to13 c constantly irradiate different positions on the spatial lightmodulation element 5 without right-up parts of the respective tracks Ta,Tb and Tc crossing each other as shown in FIG. 20.

At this time, the timing controller 16 turns on or off switchingelements at the positions of the spatial light modulation element 5irradiated with the respective linear beams 13 a to 13 c in accordancewith the video signals corresponding to the colors of the linear beams13 a to 13 c, whereby an image is displayed on the screen 7. Thus,bright red, green and blue lines are displayed on the screen 7 moment bymoment, but the red, green and blue images are simultaneously projectedonto the screen 7 by the afterimage effect by scanning the respectivelinear beams 13 a to 13 c at high speeds, wherefore a full color imagecan be displayed.

Another feature of this embodiment is that the emission periods La toLc, during which the respective linear beams 13 a to 13 c are emitted,are sufficiently longer than periods, during which they are not emitted,to enable the display of a bright image. For example, according to amethod for successively displaying a red image, a green image and a blueimage on the entire surface of the spatial light modulation element 5and causing the red, green and blue light sources to successivelyirradiate the entire surface of the spatial light modulation element 5in synchronism with a displayed image, a time during which therespective light sources are turned on is ⅓ or less than the entire timeand average outputs of the respective light sources becomes ⅓ or lessthan the maximum outputs of the respective light sources. On thecontrary, in this embodiment, the respective laser light sources 1 a to1 c are turned on during most of the time except periods during whichthe beams move from the scan ending positions to the scan startingpositions at high speeds as can be understood from FIG. 20. Therefore,average outputs substantially equal to the maximum outputs of therespective laser light sources 1 a to 1 c can be obtained for therespective laser light sources 1 a to 1 c.

The linear beams 13 a to 13 c are preferably scanned with equal andstable amplitude as shown in FIG. 20. To this end, in this embodiment,the photodetector 17 (see FIG. 18) for detecting the linear beams 13 ato 13 c is provided at a position near the spatial light modulationelement 5 and outside the display range of the spatial light modulationelement 5. By the control of the MEMS mirror 9 by the timing controller16 in accordance with a detection signal of the photodetector 17, thescan ranges and the scan speeds of the respective light beams can beaccurately controlled. As a result, color balance can be accuratelycontrolled, light utilization efficiency is increased because of noexcessive scanning to enable the display of bright images and it can beprevented that the scan angle and the scan speed vary due to an ambienttemperature change.

The photodetector 17 may not be provided near the spatial lightmodulation element 5 and may be provided at any position between theMEMS mirror 9 and the projection lens 6. Further, a beam splittingmember may be provided at any position between the MEMS mirror 9 and theprojection lens 6 and the photodetector 17 may be provided at adifferent position between the MEMS mirror 9 and the projection lens 6.

FIG. 21 is a diagram showing an example of the configuration of thedisplay region on the spatial light modulation element 5 shown in FIG.18. When the respective linear beams 13 a to 13 c are scanned on thespatial light modulation element 5 as described above, the region on thespatial light modulation element 5 is divided into a red image displayregion Ra used for the display of the red image 14 a, a green imagedisplay region Rb used for the display of the green image 14 b and ablue image display region Rc used for the display of the blue image 14c. The red linear beam 13 a is located at the central position of thered image display region Ra, the green linear beam 13 b is located atthe central position of the green image display region Rb and the bluelinear beam 13 c is located at the central position of the blue imagedisplay region Rc.

Here, it is preferable to set black display regions Rd not used for theimage display between the red image display region Ra, the green imagedisplay region Rb and the blue image display region Rc. Although therespective linear beams 13 a to 13 c have substantially linear shapes onthe spatial light modulation element 5, minimal stray lights spread in adirection of the line width (width in a shorter-side direction) BW ofthe linear beams 13 a to 13 b due to diffuse reflection in the diffusionplate 3 or the like and some of them reach the other adjacent colorimage display regions beyond the image display regions Ra to Rc. Sincedifferent colors are mixed by these stray lights, pure color cannot bedisplayed.

Accordingly, in this embodiment, the black display regions Rd areprovided between the red, green and blue image display regions Ra, Rband Rc as shown in FIG. 21. The spatial light modulation element 5 cutsoff the stray lights spreading in the line width direction in the blackdisplay regions Rd by turning off the switching elements located in theblack display regions Rd, wherefore pure colors can be respectivelydisplayed in the red, green and blue image display regions Ra, Rb and Rcand the saturations of the respective colors can be improved. Regions Reat the opposite ends in FIG. 21 may also be used as the black displayregions.

Another feature of this embodiment is that the width BW (see FIG. 21) ofthe linear beams 13 a to 13 c is 1/10 or less of the scan range SW (seeFIG. 20) in the scan direction of the linear beams 13 a to 13 c. If thelinear beams 13 a to 13 c have a definite width, the linear beams 13 ato 13 c need to be scanned in a range larger than the spatial lightmodulation element 5 in order to make an illuminance distribution on thespatial light modulation element 5 uniform. If the scan range SW isnarrower than the width (width in a longer-side direction) MW (see FIG.21) of the spatial light modulation element 5, illuminance is dark atthe opposite end portions of the spatial light modulation element 5 thatserve as the scan starting position and the scan ending position. Inorder to prevent illuminance decreases at the end portions, the linearbeams 13 a to 13 c may be scanned in a range wider than the width MW ofthe spatial light modulation element 5.

More specifically, the linear beams 13 a to 13 c may be scanned by adistance expressed by a sum (MW+BW) of the width MW of the spatial lightmodulation element 5 and the width BW of the linear beams 13 a to 13 c.At this time, light utilization efficiency decreases since the linearbeams 13 a to 13 c irradiate an area wider than the spatial lightmodulation element 5. However, if the width BW of the linear beams 13 ato 13 c is 1/10 or less of the scan range SW in the scan direction ofthe linear beams 13 a to 13 c as in this embodiment, a decrease in thelight utilization efficiency caused by the irradiation of such an areaoutside the spatial light modulation element 5 is 10% or less, whereforea decrease in brightness caused by the efficiency decrease can beprevented.

The line width BW of the linear beams 13 a to 13 c preferably satisfiesa relationship BW<SW/(2n) if SW, n denote the scan width of the linearbeams 13 a to 13 c and the number of the laser light sources (e.g. 3 inthis embodiment). In this case, the spacing between the adjacent linearbeams 13 a to 13 c is SW/n and the line width BW of the linear beams 13a to 13 c is smaller than half the spacing. By using the linear beams 13a to 13 c having the narrow line width BW in this way, it becomespossible to suppress a percentage that stray lights caused by thediffuse reflection in the diffusion plate 3 and the like enter the imagedisplay regions of the adjacent colors. Therefore, pure colors can berespectively displayed in the red, green and blue image display regionsRa, Rb and Rc and the color saturations of the respective colors can beimproved.

The scan direction of the linear beams 13 a to 13 c on the spatial lightmodulation element 5 is preferably parallel to the longer sides (sideshaving a length MW) of the display range of the spatial light modulationelement 5 as shown in FIG. 21. Since the respective linear beams 13 a to13 c can be widely spaced apart on the spatial light modulation element5 in this case, it becomes possible to suppress a percentage that straylights caused by the diffuse reflection in the diffusion plate 3 and thelike enter the image display regions of the adjacent colors, pure colorscan be respectively displayed in the red, green and blue image displayregions Ra, Rb and Rc and the color saturations of the respective colorscan be improved.

Still another feature of this embodiment is that the laser light sources1 a to 1 c are used as light sources. In recent years, theminiaturization and streamlining of ultrahigh pressure mercury lamps andmetal halide lamps have been significant. The sizes of light emissionpoints of these light sources are determined by an arc discharge lengthand are about 1 mm. Thus, in a 2-dimensional image display device usinglamp light sources, light beams of three colors cannot be irradiated onone spatial light modulation element in an efficiently divided manner,which has caused a problem of lower light utilization efficiency. On thecontrary, since laser light sources having high directivities are usedas the laser light sources 1 a to 1 c in this embodiment, lights fromthe respective laser light sources 1 a to 1 c can be converted intonarrow linear beams 13 a to 13 c to irradiate the same spatial lightmodulation element 5.

The schematic constructions of the optical system of the 2-dimensionalimage display device shown in FIG. 18 in horizontal direction and invertical direction are shown in FIGS. 22 and 23. As shown in FIGS. 22and 23, a condenser lens 2 is used to condense a divergent light fromthe laser light source 1. The light converted into a substantiallyconvergent beam by the condenser lens 2 is converted into a divergentbeam by a concave lens 8 in horizontal direction as shown in FIG. 22.The concave lens 8 is made of a cylindrical lens and has no lens powerin vertical direction and the convergent beam passes through the concavelens 8 as it is as shown in FIG. 23. The light beam converted into thedivergent beam by the concave lens 8 is converted into a parallel beamor a slightly convergent beam by the field lens 4 to propagate towardthe aperture of the projection lens 6 after being reflected by the MEMSmirror 9. Thus, there is no vignetting in the projection lens 6 andlight utilization efficiency improves. The above condenser lens 2 andfield lens 4 are not shown in FIG. 18 for simplicity.

Another feature of this embodiment is to effectively suppress thespeckle noise by scanning the linear beams 13 a to 13 c. The diffusionplate 3 is disposed before and proximate to the spatial light modulationelement 5. The diffusion plate 3 is, for example, a ground glasssubstrate having a convexo-concave pattern formed on the top surface ofa transparent glass substrate or resin substrate, gives a random phasedistribution to the wavefront of an incident light and converts anincident beam into a divergent beam.

Here, the linear beams 13 a to 13 c move on the diffusion plate 3 as thelight beam is scanned by the MEMS mirror 9. At this time, the incidenceangle of the light incident on the spatial light modulation element 5changes and, consequently, the incidence angle of the light incident onthe screen 7 changes to change the pattern of the speckle noise. Byscanning the linear beams 13 a to 13 c at high speeds, the pattern ofthe speckle noise sensed by an observer changes at a high speed and istime-averaged, whereby a high quality image free from speckle noise isobserved.

An f-number corresponding to the diffusion angle of the diffusion plate3 is preferably equal to or larger than an f-number at the incidenceside of the projection lens 6. Specifically, in a normal projector, thef-number at the incidence side of the projection lens 6 is about 1.4 to2.5. At this time, the diffusion angle of the diffusion plate 3 ispreferably 42° to 23° respectively with the full-angle-half-power. Ifthe diffusion angle exceeds this range, lights diffused at large anglesout of those diffused by the diffusion plate 3 cannot pass through theaperture of the projection lens 6 to reduce light utilizationefficiency.

Although the cylindrical lens 8 in the form of the concave lens is usedas a 1-dimensional beam expanding member for expanding the emissionlights from the laser light sources 1 a to 1 c in a 1-dimensionaldirection in the above description, a beam splitting member using agrating may also be used as in the above second embodiment. At thistime, the linear beams on the spatial light modulation element 5 becomea 1-dimensional spot array. A holographic element designed to have asuitable phase distribution determined by the cross-sectional shape(generally called a CGH (computer generated hologram)) is similarlyusable as the 1-dimensional beam expanding member for converting anincident beam into a 1-dimensional spot array. Further, a lenticularlens may be similarly used. Although the concave lens 8 as a lighttransmitting element shown in FIGS. 18 and 22 is used in thisembodiment, light reflecting elements such as concave mirrors may beused as the above cylindrical lens, the grating member and the1-dimensional beam expanding member such as a CGH.

Still another feature of this embodiment is to use the spatial lightmodulation element 5 whose elements have switching speeds of 5.5milliseconds or faster. A frame repetition frequency of a normal videomotion signal is 30 frames per second, and videos to be displayed by therespective elements of the spatial light modulation element 5 switch atleast 90 times per second when full color moving images are displayedusing the laser light sources 1 a to 1 c of three colors. In otherwords, videos are switched at every interval of 11 milliseconds. If theswitching speed of the spatial light modulation element 5 is slow,crosstalks between the video signals of the respective colors appear,causing color shifts and color fading. On the other hand, in thisembodiment, the switching can be completed when laser beams of therespective colors are irradiated and desired color moving images freefrom color shifts and color fading can be displayed by using the spatiallight modulation element 5 having a switching time of 5.5 millisecondsor shorter, which is half the above switching time.

The switching speed of the respective elements of the spatial lightmodulation element 5 is more preferably 1.8 milliseconds or faster. Outof 30 color images displayed every second, images of the respectivecolors are preferably simultaneously displayed. However, the displaytimings of the images of the respective colors are slightly shifted inthis embodiment where the images of the respective colors are displayedwhile the beams of the respective colors scan different positions on thespatial light modulation element 5. Thus, a phenomenon in which colorshifts are seen at moving contours is likely to occur upon displayingmoving images representing intense motions. On the other hand, the colorshifts of the contours can be prevented by repeatedly displaying thesame image a plurality of times. Actually, when the same image wasrepeatedly displayed three or more times, i.e. when 90 frames weredisplayed per second for the images of the three colors, there were nomore color shifts of the contours. By using the spatial light modulationelement 5 whose elements have a switching speed of 1.8 milliseconds orfaster, this display method can be realized and moving images having nocolor shifts of contours can be displayed.

Further, in the case of displaying interlaced color moving images, theswitching speed of the respective elements of the spatial lightmodulation element 5 is preferably 2.7 milliseconds or faster. At thetime of the interlaced display of video motion signals of 30 frames persecond, 60 images are switched per second. At the time of displayingfull color moving images using the laser light sources 1 a to 1 c ofthree colors, videos to be displayed by the respective elements of thespatial light modulation element 5 are switched at least 180 times persecond. In other words, videos are switched at every interval of 5.5milliseconds. If the switching speed of the spatial light modulationelement 5 is slow, crosstalks between the video signals of therespective colors appear, causing color shifts and color fading. On theother hand, the switching can be completed when laser beams of therespective colors are irradiated and desired interlaced color movingimages free from color shifts and color fading can be displayed by usingthe spatial light modulation element 5 having a switching time of 2.7milliseconds or shorter, which is half the above switching time.

The switching speed of the respective elements of the spatial lightmodulation element 5 is more preferably 0.9 milliseconds or faster. Inthe case of using the spatial light modulation element 5 whose elementshave a switching speed of 0.9 milliseconds or faster, the same image canbe repeatedly displayed three or more times, wherefore interlaced movingimages free from color shifts in contours can be displayed.

A liquid crystal element using a ferroelectric liquid crystal ispreferably used as the spatial light modulation element having a highswitching speed as described above. Although the transmission-typespatial light modulation element 5 is used in this embodiment, aso-called LCOS device constructed such that a reflection film is formedon a silicon substrate and a liquid crystal element is further mounted,a so-called DLP device constructed such that the direction of areflected light is controlled to form a light switch array by vibratinga micromirror made of a MEMS mirror or the like, or a light switch arrayhaving another arbitrary construction can be similarly used.

The diffusion plate used in this embodiment is not particularly limitedto the above example, and a pseudo random diffusion plate describedbelow may also be used. FIG. 24 is a diagram showing an example of apseudo random diffusion plate used in the 2-dimensional image displaydevice shown in FIG. 18.

The diffusion plate 3 shown in FIG. 18 is fabricated by randomlyroughening the top surface of a transparent substrate normally made ofglass, resin or the like, whereas the pseudo random diffusion plate 3 bshown in FIG. 24 is fabricated by forming a latticed convexo-concavepattern on the top surface of a transparent substrate. The top surfaceof the pseudo random diffusion plate 3 b is divided into 2-dimensionallatticed cells CE, and the depths of the convexo-concave pattern arerandomly set so that the phases of lights passing through the respectivecells CE randomly change. The maximum depth may be set to (/(n−1).

The advantage of using the pseudo random diffusion plate 3 b shown inFIG. 24 is that a diffusion angle of the light passing through thepseudo random diffusion plate 3 can be strictly controlled by the sizeof the cells. Specifically, the light is diffused to have an intensitydistribution I(( )=(sin(( )/((2((=((de/(((( )) if dc and (denote thecell interval of the latticed cells and an angle. For example, in orderto fabricate a diffusion plate whose full-angle-half-power is 10(, I(()=½ is substituted into the above equation to obtain the cell intervaldc corresponding to a wavelength (. In the case of using blue, green andred light sources having wavelengths (=0.473, 0.532 and 0.640micrometers respectively, fabrication may be made to have cell intervalsdc of 2.4, 2.7 and 3.2 micrometers respectively.

On the other hand, since the surface shapes of normal diffusion platesare random, there are problems that (1) light utilization efficiencydecreases because diffusion angles locally differ depending on spots,(2) intensity distribution nonuniformity appears in an image becausetransmittance changes depending on spots and (3) it is difficult tostably fabricate in such a manner as to have a constant diffusion angle.The normal diffusion plates have another problem of disrupting adeflection direction when a large diffusion angle is taken. The pseudorandom diffusion plate 3 b shown in FIG. 24 can solve these problems.

The pseudo random diffusion plate 3 b of FIG. 24 can be fabricated byforming a convexo-concave pattern on a glass plate by a photolithographymethod and an etching method used in a normal semiconductor process. Atthis time, if a phase transition is selected to be, for example, 0, π/2,π, 3π/2 as in FIG. 24, the pseudo random diffusion plate 3 b can beeasily fabricated by two etching processes corresponding to the phasetransitions to π/2 and to π.

Ninth Embodiment

Next, a ninth embodiment of the present invention is described. FIGS. 25and 26 are diagrams showing the schematic constructions of an opticalsystem of a 2-dimensional image display device according to the ninthembodiment of the present invention in horizontal direction and invertical direction. Since the 2-dimensional image display deviceaccording to the ninth embodiment is the same as the one according tothe eighth embodiment except that first and second field lens 4 a, 4 bshown in FIGS. 25 and 26 are used instead of the field lens 4 shown inFIGS. 22 and 23, the same parts are neither shown nor described indetail.

As shown in FIGS. 25 and 26, in this embodiment, a laser light source 1,a condenser lens 2, a concave lens 8, a MEMS mirror 9, the first fieldlens 4 a, the second field lens 4 b, a diffusion plate 3, a spatiallight modulation element 5 and a projection lens 6 are arranged in thisorder, and the concave lens 8 converts a light, which was converted intoa substantially convergent beam by the condenser lens 2, into adivergent beam in horizontal direction as shown in FIG. 25.

Here, the first field lens 4 a is made of a cylindrical lens having aconvex part in vertical direction, and the second field lens 4 b is madeof a convex lens. Accordingly, as shown in FIG. 25, the first field lens4 a has no lens power in horizontal direction (expanding direction), andthe light beam expanded by the concave lens 8 passes through the firstfield lens 4 a as it is, is suitably condensed by the second field lens4 b to be introduced to the diffusion plate 3 and the spatial lightmodulation element 5. On the other hand, as shown in FIG. 26, the firstfield lens 4 a has a lens power in vertical direction (direction normalto the expanding direction), and the light beam having passed throughthe concave lens 8 as it is sufficiently condensed by the first andsecond field lens 4 a, 4 b to be introduced to the diffusion plate 3 andthe spatial light modulation element 5. The lens power of the field lensportion made up of the first and second field lenses 4 a, 4 b in theexpanding direction is set smaller than the lens power in a directionnormal to the expanding direction. The number of lenses constituting thefield lens portion is not particularly limited to the above example, andone, three or more lenses may be used.

Accordingly, in this embodiment, effects similar to those of the eighthembodiment can be obtained, and the light beam expanded at a smallexpansion angle can be suitably condensed and suitably irradiated ontothe spatial light modulation element 5 using the first and second fieldlenses 4 a, 4 b having a small lens power in the expanding direction inthe case where the laser light source 1, the concave lens 8, the MEMSmirror 9, the first and second field lenses 4 a, 4 b, the diffusionplate 3 and the spatial light modulation element 5 are arranged in thisorder and the expansion angle of the light beam by the concave lens 8 issmall.

Tenth Embodiment

Next, a tenth embodiment of the present invention is described. FIGS. 27and 28 are diagrams showing the schematic constructions of an opticalsystem of a 2-dimensional image display device according to the tenthembodiment of the present invention in horizontal direction and invertical direction. Since the 2-dimensional image display deviceaccording to the tenth embodiment is the same as the one according tothe eighth embodiment except that first and second field lens 4 c, 4 dshown in FIGS. 27 and 28 are used instead of the field lens 4 shown inFIGS. 22 and 23 and a concave lens 8 is arranged between a MEMS mirror 9and the first field lens 4 c, the same parts are neither shown nordescribed in detail.

As shown in FIGS. 27 and 28, in this embodiment, a laser light source 1,a condenser lens 2, the MEMS mirror 9, a concave lens 8, the first fieldlens 4 c, the second field lens 4 d, a diffusion plate 3, a spatiallight modulation element 5 and a projection lens 6 are arranged in thisorder, and the concave lens 8 converts a light, which was converted intoa substantially convergent beam by the condenser lens 2 and scanned bythe MEMS mirror 9, into a divergent beam in horizontal direction asshown in FIG. 27.

Here, the first field lens 4 c is made of a cylindrical lens having aconvex part in horizontal direction, and the second field lens 4 d ismade of a convex lens. Accordingly, as shown in FIG. 27, the first fieldlens 4 c has a lens power in horizontal direction (expanding direction),and the light beam scanned by the MEMS mirror 9 is sufficientlycondensed by the first and second field lenses 4 c, 4 d to be introducedto the diffusion plate 3 and the spatial light modulation element 5after being expanded by the convex lens 8. On the other hand, as shownin FIG. 28, the first field lens 4 c has no lens power in verticaldirection (direction normal to the expanding direction), and the lightbeam having passed through the concave lens 8 as it is passes throughthe first field lens 4 c as it is and is suitably condensed by thesecond field lens 4 d to be introduced to the diffusion plate 3 and thespatial light modulation element 56. In this way, the lens power of thefield lens portion made up of the first and second field lenses 4 c, 4 din the expanding direction is set larger than the lens power in thedirection normal to the expanding direction. The number of lensesconstituting the field lens portion is not particularly limited to theabove example, and one, three or more lenses may be used.

Accordingly, in this embodiment, effects similar to those of the eighthembodiment can be obtained, and the light beam expanded at a largeexpansion angle can be suitably condensed and suitably irradiated ontothe spatial light modulation element 5 using the first and second fieldlenses 4 c, 4 d having a large lens power in the expanding direction inthe case where the laser light source 1, the MEMS mirror 9, the concavelens 8, the first and second field lenses 4 c, 4 d, the diffusion plate3 and the spatial light modulation element 5 are arranged in this orderand the expansion angle of the light beam by the concave lens 8 islarge.

Although the projection display in which the projection optical systemand the screen are separate is used as an example in the abovedescription, the present invention is also applicable to rear-projection2-dimensional image display devices in which a projection optical systemand a transmission screen are combined and 2-dimensional image displaydevices of the type in which a spatial light modulation elementilluminated by a laser from the rear side is directly observed (e.g.liquid crystal televisions presently in practical use).

As described above, the above respective 2-dimensional image displaydevices can display high-quality full color videos with less specklenoise by a simple construction and using a smaller number of parts whileusing the laser light sources, and can be utilized as projection systemor rear-projection displays.

Although the color image display devices were described as examples, thepresent invention is also applicable to image projectors using amonochromatic laser, exposure illumination devices used, for example, insemiconductor processes or their light source devices. In an exposureillumination device, an ultraviolet laser is used as a laser lightsource, a photomask or the like formed, for example, by patterning ametal film on a glass substrate is used as a spatial light modulationelement, and a mask pattern image is formed on a semiconductor substrateas a screen.

As described above, a 2-dimensional image display device according toone aspect of the present invention comprises at least one laser lightsource; a beam scan unit for converting an emission beam from the laserlight source into a 2-dimensional light while scanning the emission beamat least in a 1-dimensional direction; a spatial light modulationelement for spatially modulating the light scanned by the beam scanunit; and a light diffusion member disposed between the beam scan unitand the spatial light modulation element for diffusing the 2-dimensionallight emerging from the beam scan unit.

Since the emission beam from the laser light source is converted intothe 2-dimensional light while being scanned at least in the1-dimensional direction in this 2-dimensional image display device,uniform illumination can be obtained. Further, since the light diffusionmember is disposed between the beam scan unit and the spatial lightmodulation element and the 2-dimensional light emerging from the beamscan unit is diffused and irradiated onto the spatial light modulationelement, the optical axis of the beam emerging from the light diffusionmember to irradiate the spatial light modulation element can be changedmoment by moment and speckle noise can be effectively suppressed. As aresult, a beam expander, a light integrator and the like for uniformillumination become unnecessary, and uniform illumination can beobtained and the speckle noise can be effectively suppressed using asimple optical system.

It is preferable that the beam scan unit includes a 2-dimensionalscanning portion for scanning the emission beam from the laser lightsource in a first direction and a second direction normal to the firstdirection; and that the 2-dimensional scanning portion cyclically scansthe light beam incident on the light diffusion member at a frequency atwhich a ratio of a scan frequency in the first direction to a scanfrequency in the second direction is a ratio of integers prime to eachother.

In this case, the beam incident on the light diffusion member iscyclically scanned at the frequency at which the ratio of the scanfrequency in the first direction to the scan frequency in the seconddirection is the ratio of integers prime to each other upon scanning theemission beam from the laser light source in the mutually orthogonalfirst and second directions. Thus, a difference between the scan speedsin the first and second directions can be made smaller, the constructionof the 2-dimensional beam scanning portion can be simplified and thelight diffusion member can be uniformly illuminated.

The beam scan unit preferably includes a 1-dimensional beam splittingportion for splitting the emission beam from the laser light source togenerate a 1-dimensional multibeam array in which a plurality of beamsare arrayed in a first direction and a 1-dimensional scanning portionfor scanning the 1-dimensional multibeam array in the second directionnormal to the first direction.

In this case, the miniaturization, lower power consumption and lowercost of the 1-dimensional beam splitting portion can be realized sincethe scan direction is 1-dimensional and the scan frequency is low.

The 1-dimensional beam splitting portion preferably has first and secondsplitting surfaces for splitting the emission beam from the laser lightsource at different intervals.

In this case, since light intensity distributions of the 1-dimensionalmultibeam arrays split at different intervals are combined, thenonuniformity of the light intensity distribution caused by a0^(th)-order diffracted light can be reduced.

The beam scan unit preferably includes a 2-dimensional beam splittingportion for splitting the emission beam from the laser light source in afirst direction and a second direction normal to the first direction togenerate a 2-dimensional multibeam in which a plurality of beams are2-dimensionally arrayed, and a fine scanning portion for finely scanningthe 2-dimensional multibeam.

In this case, the miniaturization, lower cost, lower power consumptionand lower noise of the fine scanning portion can be realized since thescan angle of the 2-dimensional multibeam can be made smaller.

The 2-dimensional beam splitting portion preferably includes a first1-dimensional beam splitting portion for splitting the emission beamfrom the laser light source to generate a 1-dimensional multibeam arrayin which a plurality of beams are arrayed in a first direction, and asecond 1-dimensional beam splitting portion for splitting the1-dimensional multibeam array generated by the first 1-dimensional beamsplitting portion in a second direction normal to the first direction togenerate a 2-dimensional multibeam.

In this case, the nonuniformity of a light intensity distribution causedby a 0^(th)-order diffracted light can be reduced since the matrix-like2-dimensional multibeam arrayed in the mutually orthogonal first andsecond directions is generated.

The 2-dimensional beam splitting portion preferably includes a2-dimensional diffraction grating having inclined grating surfaces.

In this case, the 0^(th)-order diffracted light and diffracted lightsother than the 0^(th)-order diffracted light can be split, therebycausing the diffracted lights other than the 0^(th)-order diffractedlight to irradiate the light diffusion member and the spatial lightmodulation element while preventing the 0^(th)-order diffracted lightfrom irradiating the light diffusion member and the spatial lightmodulation element. Therefore, a light intensity distribution on thespatial light modulation element can be made more uniform.

The beam scan unit preferably includes a vibrating portion for vibratinga 2-dimensional beam splitting portion for splitting the emission beamfrom the laser light source in a first direction and a second directionnormal to the first direction to generate a 2-dimensional multibeam inwhich a plurality of beams are 2-dimensionally arrayed.

In this case, the number of parts can be reduced and the device can befurther miniaturized since the 2-dimensional beam splitting portion isconstructed integral to the vibrating portion.

It is preferable to further comprise reflection mirrors for surroundingan optical path between the beam scan unit and the light diffusionmember and introducing a light beam from the beam scan unit to the lightdiffusion member after reflecting it a plurality of times.

In this case, since the optical path between the beam scan unit and thelight diffusion member is covered by the reflection mirrors, the loss ofthe light beam can be prevented in this part to improve the lightintensity distribution on the spatial light modulation element.

The reflection mirrors preferably further surround an optical pathbetween the light diffusion member and the spatial light modulationelement.

In this case, since the optical path between the light diffusion memberand the spatial light modulation element is further covered by thereflection mirror, the loss of the light beam can be prevented also inthis part to improve the light intensity distribution on the spatiallight modulation element.

The laser light source preferably includes three laser light sources forgenerating red, green and blue colors.

In this case, a vivid image having high color purity can be displayedusing red, green and blue lights, and a dichroic mirror and the like formultiplexing become unnecessary, thereby being able to simplify theoptical system.

The light diffusion member and the spatial light modulation element arepreferably in a one-to-one correspondence with each of the three laserlight sources.

In this case, since the light is diffused for each color of the threelaser light sources and the spatial light modulation elements can beindividually controlled, a more vivid image having higher color puritycan be displayed using the light diffusion members and the spatial lightmodulation elements suited to the wavelengths of the respective colors.

Emission beams from the three laser light sources are preferablyincident on the beam scan unit at mutually different angles.

In this case, a dichroic mirror and the like for multiplexing becomeunnecessary and a 2-dimensional image display device can be realized bya simple optical system.

The light diffusion member preferably includes a pseudo random diffusionplate.

In this case, since a convexo-concave pattern for diffusing a light canbe regularly formed, the light can be more uniformly diffused to improvelight utilization efficiency, the nonuniformity of the light intensitydistribution can be suppressed, fabrication can be stably made such thata diffusion angle is constant, and a deflection direction can beaccurately controlled even if a large scattering angle is taken.

The beam scan unit preferably includes a beam expanding portion forexpanding the emission beam from the laser light source in a firstdirection to generate a linear beam and a 1-dimensional scanning portionfor scanning the linear beam in a second direction normal to the firstdirection.

In this case, since the scan direction is 1-dimensional and the scanfrequency is small, the miniaturization, lower power consumption andlower cost of the 1-dimensional beam scan unit can be realized.

It is preferable that a field lens portion is further provided betweenthe 1-dimensional scanning portion and the light diffusion member; thatthe laser light source, the beam expanding portion, the 1-dimensionalscanning portion, the field lens portion, the light diffusion member andthe spatial light modulation element are arranged in this order; andthat a lens power of the field lens portion in the first direction issmaller than the one in the second direction.

In this case, since a light beam expanded at a small expansion angle canbe suitably condensed, the light beam can be suitably irradiated ontothe spatial light modulation element.

It is preferable that the beam scan unit includes a 1-dimensionalscanning portion for scanning the emission beam from the laser lightsource in a first direction and a beam expanding portion for expandingthe light beam scanned by the 1-dimensional scanning portion in a seconddirection normal to the first direction to generate a linear beam; thata field lens portion is further provided between the beam expandingportion and the light diffusion member; that the laser light source, the1-dimensional scanning portion, the beam expanding portion, the fieldlens portion, and the spatial light modulation element are arranged inthis order; and that a lens power of the field lens portion in the firstdirection is smaller than the one in the second direction.

In this case, since the scan direction is 1-dimensional and the scanfrequency is small, the miniaturization, lower power consumption andlower cost of the 1-dimensional beam scanning portion can be realized.In addition, since the light beam expanded at a large expansion anglecan be sufficiently condensed, the light beam can be suitably irradiatedonto the spatial light modulation element.

It is preferable that the laser light source includes a plurality oflaser light sources; and that linear beams from the plurality of laserlight sources illuminate different positions on the spatial lightmodulation element.

In this case, a plurality of colors can be combined using one spatiallight modulation element, and a dichroic mirror and the like formultiplexing become unnecessary, thereby being able to simplify theoptical system.

The spatial light modulation element preferably modulates the respectivelinear beams from the plurality of laser light sources such thatdifferent videos corresponding to the respective linear beams aredisplayed in image display regions irradiated with the respective linearbeams.

In this case, images of a plurality of colors can be combined using onespatial light modulation element.

It is preferable to set black display regions not transmitting thelinear beams between the adjacent image display regions on the spatiallight modulation element.

In this case, since stray lights of the linear beams spreading in a linewidth direction can be cut off by the black display regions, pure colorscan be displayed in the image display regions of the respective colorsand the color saturations of the respective colors can be improved.

A width BW of the linear beams in a shorter-side direction on thespatial light modulation element preferably satisfies a relationshipBW<SW/10 if SW denotes a scan width of the linear beams.

In this case, illuminance decreases at end portions of the spatial lightmodulation element that serve as a scan starting position and a scanending position can be prevented while suppressing a decrease in lightutilization efficiency caused by irradiating a region outside thespatial light modulation element.

A width BW of the linear beams in a shorter-side direction on thespatial light modulation element preferably satisfies a relationshipBW<SW/(2n) if SW, n denote a scan width of the linear beams and thenumber of the plurality of laser light sources.

In this case, pure colors can be displayed in image display regions ofthe respective colors and the color saturations of the respective colorscan be improved since a percentage that stray lights caused by diffusereflection in the light diffusion member enter the adjacent imagedisplay regions can be suppressed.

It is preferable that the plurality of laser light sources include afirst laser light source for emitting a red light, a second laser lightsource for emitting a green light and a third laser light source foremitting a blue light; and that the spatial light modulation elementmodulates linear beams such that a red image is displayed in a red imagedisplay region irradiated with linear beams from the first laser lightsource, a green image is displayed in a green image display regionirradiated with linear beams from the second laser light source and ablue image is displayed in a blue image display region irradiated withlinear beams from the third laser light source.

In this case, a full color video can be displayed using one spatiallight modulation element.

The switching speed of the spatial light modulation element ispreferably 5.5 milliseconds or faster.

In this case, desired color moving images free from color shifts andcolor fading can be displayed since the switching can be completed whenthe laser beams of the respective colors are irradiated.

The switching speed of the spatial light modulation element ispreferably 2.7 milliseconds or faster.

In this case, desired interlaced color moving images free from colorshifts and color fading can be displayed since, upon displayinginterlaced color moving images, the switching can be completed when thelaser beams of the respective colors are irradiated.

The switching speed of the spatial light modulation element ispreferably 1.8 milliseconds or faster.

In this case, moving images whose contours are free from color shiftscan be displayed since the same image can be repeatedly displayed threeor more times.

The switching speed of the spatial light modulation element ispreferably 0.9 milliseconds or faster.

In this case, interlaced moving images whose contours are free fromcolor shifts can be displayed since the same image can be repeatedlydisplayed three or more times upon displaying interlaced color movingimages.

The spatial light modulation element is preferably made of aferroelectric liquid crystal.

In this case, moving images as described above can be satisfactorilydisplayed since the switching speed can be set high.

The spatial light modulation element preferably includes a plurality of2-dimensionally arrayed MEMS mirrors.

In this case as well, moving images as described above can besatisfactorily displayed since the switching speed can be set high.

Scan directions of lights from the plurality of laser light sources onthe spatial light modulation element are preferably parallel to thelonger sides of a display region of the spatial light modulationelement.

In this case, since the lights from the respective laser light sourcescan be widely spaced apart on the spatial light modulation element, apercentage that stray lights caused by diffuse reflection in the lightdiffusion member enter the adjacent image display regions can besuppressed, pure colors can be displayed in the image display regions ofthe respective colors and the color saturations of the respective colorscan be improved.

The light diffusion member preferably includes a pseudo random diffusionplate in which rectangular cells are 2-dimensionally arrayed, the cellsshift the phases of lights passing therethrough and a difference inphase displacements between the adjacent cells is π/2.

In this case, the light can be more uniformly diffused to improve lightutilization efficiency and the nonuniformity of the light intensitydistribution can be suppressed since a convexo-concave pattern fordiffusing the light can be regularly formed. Further, fabrication can bestably made to make a diffusion angle constant and, even if a largediffusion angle is taken, a deflection direction can be accuratelycontrolled. Furthermore, easy fabrication is possible by reducing thenumber of etching processes.

A light beam diameter S on the light diffusion member preferablysatisfies a relationship S>L·θ−d if θ, L and d denote the diffusionangle of the light diffusion member, a distance between the lightdiffusion member and the spatial light modulation element and thespacing between the adjacent light beams on the spatial light modulationelement.

In this case, speckle noise can be further reduced since any arbitrarypoint on the spatial light modulation element can be illuminated by adiffused light from the plurality of light beams.

The emission beam from the laser light source is preferablysubstantially condensed on the spatial light modulation element.

In this case, light utilization efficiency can be improved since thelight beam can be efficiently irradiated onto the spatial lightmodulation element.

It is preferable to further comprise a projection optical system forprojecting the light modulated by the spatial light modulation elementon a plane in a space.

In this case, a satisfactory video having the speckle noise effectivelysuppressed can be displayed on the plane in the space such as a screen.

The beam scan unit preferably includes a polarization inversion element.

In this case, a 2-dimensional image display device that is highlyreliable, silent and speedy can be provided since the beam scan unit hasno movable part.

An illumination light source according to another aspect of the presentinvention comprises at least one laser light source, a beam scan unitfor scanning an emission beam from the laser light source at least in a1-dimensional direction and a light diffusion member for diffusing theemission beam scanned by the beam scan unit.

An exposure illumination device according to still another aspect of thepresent invention comprises the above illumination light source, whereinthe laser light source includes an ultraviolet laser.

By the above respective constructions, uniform illumination can beobtained since the emission beam from the laser light source is scannedat least in the 1-dimensional direction. Further, since the emissionbeam scanned by the beam scan unit is diffused, the optical axis of thebeam emerging from the light diffusion member can be changed moment bymoment, wherefore the speckle noise can be effectively suppressed. As aresult, a beam expander, a light integrator and the like for uniformillumination become unnecessary, and uniform illumination can beobtained and the speckle noise can be effectively suppressed using asimple optical system.

INDUSTRIAL APPLICABILITY

A 2-dimensional image display device and the like according to thepresent invention can obtain uniform illumination and can effectivelysuppress the speckle noise using a simple optical system and, therefore,are suitably applicable to video display devices such as videoprojectors, television receivers and liquid crystal panels.

1-37. (canceled)
 38. A 2-dimensional image display device, comprising:at least one laser light source; a beam scan unit for converting anemission beam from said laser light source into a 2-dimensional lightwhile scanning the emission beam at least in a 1-dimensional direction;a spatial light modulation element for spatially modulating the lightscanned by said beam scan unit; and a light diffusion member disposedbetween said beam scan unit and said spatial light modulation elementfor diffusing the 2-dimensional light emerging from said beam scan unit,wherein said beam scan unit includes: a 1-dimensional beam splittingportion for splitting the emission beam from said laser light source togenerate a 1-dimensional multibeam array in which a plurality of beamsare arrayed in a first direction; and a 1-dimensional scanning portionfor scanning the 1-dimensional multibeam array in the second directionnormal to the first direction.
 39. A 2-dimensional image display deviceaccording to claim 38, wherein said 1-dimensional beam splitting portionhas first and second splitting surfaces for splitting the emission beamfrom said laser light source at different intervals.
 40. A 2-dimensionalimage display device according to claim 38, wherein said laser lightsource includes first, second and third laser light sources forgenerating red, green and blue colors, respectively.
 41. A 2-dimensionalimage display device according to claim 40, wherein said light diffusionmember is one of a plurality of diffusion members and said spatial lightmodulation element is one of a plurality of spatial light modulationelements, said plurality of diffusion members and said plurality ofspatial light modulation elements being in a one-to-one correspondencewith said laser light sources.
 42. A 2-dimensional image display deviceaccording to claim 41, wherein emission beams from said first, secondand third laser light sources are incident on said beam scan unit atmutually different angles.
 43. A 2-dimensional image display deviceaccording to claim 38, wherein a light beam diameter S on the lightdiffusion member satisfies a relationship S>L·θ−d if θ, L and d denotethe diffusion angle of said light diffusion member, a distance betweensaid light diffusion member and said spatial light modulation elementand the spacing between the adjacent light beams on said spatial lightmodulation element.
 44. A 2-dimensional image display device accordingto claim 38, wherein the emission beam from said laser light source issubstantially condensed on said spatial light modulation element.
 45. A2-dimensional image display device according to claim 38, furthercomprising a projection optical system for projecting the lightmodulated by said spatial light modulation element on a plane in aspace.